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Abstract:

Heterophasic polypropylene composition comprising (A) 45 to 70 wt % of a
propylene homo- or copolymer matrix with an MFR2 in accordance with
ISO 1133 (230° C., 2.16 kg load) of ≧80 g/10 min and (B) 25
to 40 wt % of an elastomeric propylene-ethylene copolymer, having an
intrinsic viscosity IV (ISO 1628, with decalin as solvent) of ≧
3.3 dl/g and an ethylene content of 20 to 50 wt %, (C) 0-15 wt % of an
elastomeric ethylene/alpha-olefin random copolymer (D) 3-25 parts per
weight of inorganic filler, the heterophasic polypropylene compositions
having a total MFR2 (230° C./2.16 kg) in accordance with ISO
1133 of ≧5 g/10 min, a Charpy notched impact strength according to
ISO 179/1eA at +23° C. of ≧15.0 kJ/m2, preferably
≧25.0 kJ/m2, a minimum value for the Charpy notched impact
strength according to ISO 179/1eA at -200 C of ≧7.0 kJ/m2,
preferably ≧10.0 kJ/m2 and a tensile modulus according to ISO
527-3 of ≧1200 MPa; their preparation and use for producing
injection moulded articles being free of flow marks.

Claims:

1. Heterophasic polypropylene composition comprising (A) 45 to 70 wt % of
a propylene homo- or copolymer matrix with an MFR2 in accordance
with ISO 1133 (230.degree. C., 2.16 kg load) of ≧80 g/10 min and
(B) 25 to 40 wt % of an elastomeric propylene-ethylene copolymer, having
an intrinsic viscosity IV (ISO 1628, with decalin as solvent) of
≧3.3 dl/g and an ethylene content of 20 to 50 wt %, (C) 0-15 wt %
of an elastomeric ethylene/alpha-olefin random copolymer (D) 3-25 parts
per weight of inorganic filler, the heterophasic polypropylene
compositions having a total MFR2 (230.degree. C./2.16 kg) in
accordance with ISO 1133 of ≧5 g/10 min, a Charpy notched impact
strength according to ISO 179/1eA at +23.degree. C. of ≧15.0
kJ/m2, a minimum value for the Charpy notched impact strength
according to ISO 179/1eA at -20.degree. C. of ≧7.0 kJ/m2, and
a tensile modulus according to ISO 527-3 of ≧1200 MPa.

6. Heterophasic polypropylene composition according to claim 1, wherein
said inorganic filler is selected from the group consisting of talc,
chalk, clay, mica, clay or glass fibres and carbon fibres up to a length
of 6 mm.

8. Process for the preparation of heterophasic polypropylene compositions
according to claim 1, comprising the steps of: producing a polypropylene
polymer matrix (A) in the presence of a catalyst system comprising a
Ziegler-Natta procatalyst in combination with an external donor and a
cocatalyst in at least one slurry reactor transferring the slurry reactor
product into a first gas phase reactor (GPR), wherein the slurry reactor
product is further polymerized in the presence of the catalyst system in
said first GPR transferring the first GPR product into a 2.sup.nd GPR
producing an ethylene/propylene-copolymer (B) in the polymer matrix (A)
in the presence of the catalyst system in said 2.sup.nd GPR transferring
the 2.sup.nd GPR product into a 3.sup.rd GPR and further producing an
ethylene/propylene-copolymer (B) in the polymer matrix (A) in the
presence of the catalyst system in said 3.sup.rd GPR, said
ethylene/propylene copolymers having the same composition ratios and
recovering the polymer product for further processing, yielding a
polypropylene polymer matrix (A) containing said ethylene/propylene
copolymers (B) having the same composition ratios, respectively having
same ethylene content and intrinsic viscosities, so that an unimodal
rubber composition is obtained adding (C) 0-15 wt % of an elastomeric
ethylene/alpha-olefin random copolymer and (D) 3-25 parts per weight of
inorganic filler.

9. Process according to claim 8, wherein the catalyst system used
comprises (i) a Ziegler-Natta procatalyst which contains a
trans-esterification product of a lower alcohol and a phthalic ester as
internal donor and (ii) an organometallic cocatalyst and (iii) an
external donor represented by formula (III)
Si(OCH2CH3)3(NR1R2) wherein R1 and R2
can be the same or different a represent a hydrocarbon group having 1 to
12 carbon atoms or formula (IV) R3nR4mSi(OR5)z wherein
R3 and R4 are identical or different hydrocarbon residues,
R5 is methyl or ethyl, z is 2 or 3; m is 0 or 1; n is 0 or 1; with
the proviso that n+m+z=4, said procatalyst being modified by polymerizing
it with a vinyl compound of the formula CH.sub.2.dbd.CH--CHR6R7
wherein R6 and R7 together form a 5- or 6-membered saturated,
unsaturated or aromatic ring or independently represent an alkyl group
comprising 1 to 4 carbon atoms, in the presence of the cocatalysts and
the external donor.

10. Process according to claim 9, wherein the vinyl compound used for
modifying the procatalyst is vinyl cyclohexane.

12. Injection moulded articles produced from heterophasic polypropylene
compositions comprising A 45 to 70 wt % of a propylene homo- or copolymer
matrix with an MFR in accordance with ISO 1133 (230.degree. C., 2.16 kq
load) of ≧80 q/10 min and (B) 25 to 40 wt % of an elastomeric
propylene-ethylene copolymer, having an intrinsic viscosity IV (ISO 1628,
with decalin as solvent) of ≧3.3 dl/q and an ethylene content of
20 to 50 wt %, (C) 0-15 wt % of an elastomeric ethylene/alpha-olefin
random copolymer (D) 3-25 parts per weight of inorganic filler, the
heterophasic of polypropylene compositions have a total MFR2
(230.degree. C./2.16 kg) in accordance with ISO 1133 of ≧5 g/10
min, a Charpy notched impact strength according to ISO 179/1eA at
+23.degree. C. of ≧15.0 kJ/m2, a minimum value for the Charpy
notched impact strength according to ISO 179/1eA at -20.degree. C. of
≧7.0 kJ/m2, and a tensile modulus according to ISO 527-3 of
≧1200 MPa, said injection moulded articles being free of flow
marks.

13. Heterophasic polypropylene composition according to claim 1, wherein
said Charpy notched impact strength according to ISO 179/1eA at
+23.degree. C. of is ≧25.0 kJ/m.sup.2.

14. Heterophasic polypropylene composition according to claim 1, wherein
said minimum value for the Charpy notched impact strength according to
ISO 179/1eA at -20.degree. C. is ≧10.0 kJ/m.sup.2.

15. Heterophasic polypropylene composition according to claim 1, wherein
said Charpy notched impact strength according to ISO 179/1eA at
+23.degree. C. of is ≧25.0 kJ/m2, and wherein said minimum
value for the Charpy notched impact strength according to ISO 179/1eA at
-20.degree. C. is ≧10.0 kJ/m.sup.2.

16. Process according to claim 9, wherein said z is 2.

17. Injection moulded articles according to claim 12, wherein said Charpy
notched impact strength according to ISO 179/1eA at +23.degree. C. of is
≧25.0 kJ/m.sup.2.

18. Injection moulded articles according to claim 12, wherein said
minimum value for the Charpy notched impact strength according to ISO
179/1eA at -20.degree. C. is ≧10.0 kJ/m.sup.2.

19. Injection moulded articles according to claim 12, wherein said Charpy
notched impact strength according to ISO 179/1eA at +23.degree. C. of is
≧25.0 kJ/m2, and wherein said minimum value for the Charpy
notched impact strength according to ISO 179/1eA at -20.degree. C. is
≧10.0 kJ/m.sup.2.

Description:

[0001] The present invention relates to heterophasic polypropylene
copolymer composition. The inventive heterophasic polypropylene copolymer
compositions are especially suited for the automotive applications
because they have excellent impact strength/stiffness balance, high
flowability and are not susceptible to the occurrence of flow marks.
Furthermore, the present invention relates to a process for the
production of such copolymers as well as to their use.

[0002] Heterophasic polypropylene copolymer compositions, which typically
comprise polypropylene and an elastomer, have many desirable properties,
e.g. lightweight, durability, low costs, etc. that make them an
attractive material of construction for many interior and exterior
automotive parts.

[0003] Normally such compositions are injection moulded into the desired
articles. If the articles are relatively large, such as for example
automobile bumpers, instrument panels or centre-consoles, the problem of
optical irregularity arises, due to the necessary long flow paths of the
resin.

[0004] Such surface defects, which are also known as "Tigerstripes" or
flow marks, are a common problem for surface quality respectively
appearance in plastic industry. Tigerstripes, as known in the plastic
industry, describe a visible periodic inhomogeneity in surface gloss.
Mostly these are alternating dull (or rough) and glossy (or smooth) areas
on the surface of injection molded or extruded plastic parts, which
surface should be glossy (or smooth) all over.

[0005] Many attempts to avoid these surface defects, while keeping a good
balance of other physical properties have been made in the past.

[0006] For example WO 2004/000899 describes polyolefins on the basis of a
polypropylene matrix material including bimodal rubber compositions,
whereby the two rubber parts have differentiated Mw (respectively
intrinsic viscosity IV) and the low IV rubber is ethylene rich. These
polyolefins are produced in a multistage process comprising at least one
slurry reactor and two gas phase reactors. A particularly preferred
catalyst system is, according to WO 2004/000899, a high yield
Ziegler-Natta catalyst having a catalyst component, a cocatalyst and
optionally an external donor, or a metallocene catalyst, having a bridged
structure giving high stereoregularity and which, as an active complex,
is impregnated on a carrier. The polymers produced according to WO
2004/000899 show improved surface toughness in terms of scratch
resistance and can be used for producing car interiors and exteriors,
like bumpers, dashboards and the like, where improved scratch resistance
properties are needed.

[0007] The main disadvantage of bimodal rubbers is product inconsistency
due to migration which leads to surface deposits.

[0008] Furthermore, if such materials are used for painted applications,
the low IV fraction influences the steam jet performance negatively as
the material delaminates more easily. From experience it is known that
RTPOs, produced according to WO 2004/000899 show flow marks.

[0010] The propylene polymer composition is mixed with an elastomeric
ethylene-1-octene copolymer, having an ethylene content of at least 80
mol % and having an MFR in accordance with ISO 1133 (190° C., 2.16
kg) of 3-100 g/10 min, and with an inorganic filler. These propylene
polymer compositions are, according to EP 1 600 480, suitable for
automotive applications because they have excellent impact
strength/stiffness balance, high flowability and are not susceptible to
the occurrence of flow marks.

[0011] The RTPO is produced in a multistage process using a Ziegler-Natta
catalyst. According to the examples ZN104 (commercially available from
LyondellBasell), triethylaluminium as cocatalyst and
dicyclopentyldimethoxysilane as external donor are used.

[0012] According to the Examples of EP 1 600 480 MFR-values of at most 100
g/10 min for the propylene matrix can be achieved by using this
combination of catalyst, cocatalyst and external donor, limiting the
overall processability of the related compositions.

i) 60 to 90 wt %, relative to the total weight of components i), ii) and
iii), of a propylene polymer matrix comprising a propylene homopolymer
and, optionally, a propylene copolymer, said propylene polymer matrix
having an ethylene content of no more than 5 wt %; ii) 5 to 30 wt %,
relative to the total weight of components i), ii) and iii), of an
elastomer; and iii) 5 to 25 wt %, relative to the total weight of
components i), ii) and iii), of an ethylene copolymer plastomer having a
density of not more than 910 kg/m3 and a melt flow rate MFR2.16
(190° C.) of at least 0.5 g/10 minutes at 190° C. under a
weight of 2.16 kg.

[0014] The elastomer is preferably a propylene-ethylene copolymer
containing 25 to 45 wt % ethylene and having an intrinsic viscosity (IV
of AM) of 1.5 to 4 dL/g, preferably 2 to 3.5 dL/g measured in decalin at
135° C. according to ASTM method D1601-78.

[0015] The plastomers used in the present invention may be produced for
example by metallocene-catalyzed polymerization or other single site
catalyzed polymerization.

[0016] Such compositions show decreased stress whitening, but no
indication of good surface structure and avoiding tigerstripes formation
is given.

A) a heterophasic propylene copolymer containing a) 50-95 wt % of a
matrix phase comprising a propylene homopolymer or a propylene copolymer
with up to 5 mol % of ethylene and/or at least one
C4-C8-α-olefin and b) 5-50 wt % of a disperse phase
comprising an ethylene rubber copolymer with from 20-80 mol % ethylene
and from 80-20 mol % of at least one C3-C8-α-olefin and
where the intrinsic viscosity of the XCS-fraction of the heterophasic
copolymer is ≦2 dl/g and B) a β-nucleating agent.

[0019] EP 1 607 440 describes a polypropylene composition comprising a
heterophasic propylene copolymer, an elastomeric copolymer and inorganic
filler and a method for producing the propylene composition using
peroxides. The composition is characterised by a combination of excellent
impact strength, stiffness, elasticity and surface stability having i.a.
a Charpy notched impact strength according to ISO 179/1eA at +23°
C. of ≧55.0 kJ/m2 and a tensile modulus according to ISO 527-3 of
≧1200 MPa.

[0020] As is known by art skilled persons visbreaking with peroxides
reduces especially stiffness and secondly has very negative influence on
emission, fogging and odour.

[0021] WO 00/68315 describes i.a. the preparation of a nucleated
high-stiffness heterophasic propylene polymer composition in a two-stage
polymerization process using a catalyst system comprising a catalyst
component, a cocatalyst component and an external donor, said catalyst
being modified by polymerizing it with a vinyl compound in the presence
of a cocatalysts and an external donor, which is according to the
examples preferably dicyclopentyldimethoxysilane. Such heterophasic
copolymers can have a polypropylene homopolymer matrix with a MFR2
(230° C./2.16 kg) in accordance with ISO 1133 in the range of 0.01
to 1500 g/min, preferably 0.05 to 500 g/min. According to the only
example of the application referring to heterophasic polypropylene the
intrinsic viscosity of the rubber is 4.1 dl/g, the amount of the rubber
phase is 21.7 wt %.

[0022] It has however, been found, that either the occurrence of flow
marks could not be entirely prevented, or the physical properties of the
polymer compositions were unsatisfactory.

[0023] For these reasons, although much development work has been done in
the field of heterophasic polypropylene copolymer compositions there is a
continuous need for alternative or improved heterophasic polypropylene
copolymer compositions, which can be injection moulded into large
articles, which articles show no flow marks and which compositions
simultaneously show an improved impact strength/stiffness balance.

[0024] The new compositions shall be used for injection moulding,
therefore the MFR2 (230° C./2.16 kg) in accordance with ISO
1133 of the compositions is preferred to be ≧5 g/10 min. A Charpy
notched impact strength according to ISO 179/1eA at +23° C. of
≧15.0 kJ/m2.

[0025] The minimum value for the Charpy notched impact strength according
to ISO 179/1eA at -20° C. is ≧7.0 kJ/m2. Stiffness is
considered to be high with tensile moduli according to ISO 527-3 of
≧1200 MPa. Still higher values are of course more preferable. The
surface quality of injection moulded parts, which is determined according
to the procedure described in the experimental section, must be
"excellent", i.e. only polymer compositions which can be injection
moulded without showing any flow marks, solve the problem which is
underlying the present invention.

[0026] The above object was achieved with a polypropylene polymer
composition comprising

(A) 45 to 70 wt % of a propylene homo- or copolymer matrix with an
MFR2 in accordance with ISO 1133 (230° C., 2.16 kg load) of
≧80 g/10 min and (B) 25 to 40 wt % of an elastomeric
propylene-ethylene copolymer, having an intrinsic viscosity IV (ISO 1628,
with decalin as solvent) of ≧3.3 dl/g and an ethylene content of
20 to 50 wt %, C) 0-15 wt % of an elastomeric ethylene/alpha-olefin
random copolymer D) 3-25 wt % of inorganic filler, the heterophasic
polypropylene compositions having a total MFR2 (230° C./2.16
kg) in accordance with ISO 1133 of ≧5 g/10 min, a Charpy notched
impact strength according to ISO 179/1eA at +23° C. of
≧15.0 kJ/m2, preferably ≧25.0 kJ/m2, a minimum
value for the Charpy notched impact strength according to ISO 179/1eA at
-20° C. of ≧7.0 kJ/m2, preferably ≧10.0
kJ/m2 and a tensile modulus according to ISO 527-3 of ≧1200
MPa.

[0027] Furthermore the heterophasic polypropylene compositions according
to the present invention show high flowability, measured with the spiral
flow test at 230° C., as described in the experimental part in
detail.

[0028] The polypropylene matrix (A) can be a propylene homopolymer, a
propylene copolymer or mixtures thereof, like a homo/random copolymer.
However, it is preferred that the polypropylene matrix (A) is a propylene
homopolymer.

[0029] The expression homopolymer used in the instant invention relates to
a polypropylene that consists substantially, i.e. of at least 97 wt %,
preferably of at least 98 wt %, more preferably of at least 99 wt %,
still more preferably of at least 99.8 wt % of propylene units. In a
preferred embodiment only propylene units in the propylene homopolymer
are detectable. The comonomer content can be determined with FT infrared
spectroscopy, as described below in the examples.

[0030] Where the polypropylene matrix (A) comprises a propylene copolymer
or is a homo/random propylene copolymer, the propylene copolymer
comprises monomers copolymerizable with propylene, for example comonomers
such as ethylene and C4 to C20 alpha-olefins, in particular
ethylene and C4 to C10 alpha-olefins, e.g. 1-butene or
1-hexene. The comonomer content in the propylene matrix is in such a case
preferably relatively low, i.e. up to 6.0 wt %, more preferably 1.0 to
6.0 wt %, still more preferably 1.0 to 4.0 wt %, yet more preferably 1.0
to 3.0 wt %.

[0031] The polypropylene matrix (A) is preferably unimodal, but can also
be multimodal, like bimodal. Concerning the definition of unimodal and
multimodal, like bimodal, it is referred to the definition below.

[0032] For achieving injection moulded parts free of flow marks, it is
essential, that the MFR2 in accordance with ISO 1133 (230°
C., 2.16 kg load) of the propylene matrix (A) is ≧80 g/10 min.
Preferably the propylene matrix (A) has an MFR2 (230°
C.)≧100 g/10 min, more preferably 110 g/10 min and most preferably
≧120 g/10 min. The MFR2 (230° C.) can be up to 500
g/10 min.

[0033] As a further requirement of the heterophasic polypropylene
copolymer the elastomeric copolymer must fulfill some properties so that
the desired results can be achieved.

[0034] Accordingly the elastomeric copolymer (B) must comprise propylene
and at least ethylene and may comprise a further other C4 to
C10 alpha-olefin selected from the group consisting of 1-butene,
1-pentene, 1-hexene, 1-heptene and 1-octene. However, it is in particular
preferred that the elastomeric copolymer (B) comprises, more preferably
consists of, propylene and ethylene as the only polymerizable units.

[0043] The mean particle size d50 of the filler may be chosen between 0.5
to 40 μm, preferably between 0.7 to 20 μm and more preferably
between 1.0 to 10 μm.

[0044] The mean (or median) particle size is the particle diameter where
50% of the particles are larger and 50% are smaller. It is denoted as the
d50 or D50.

[0045] In principle, this value may be determined by any particle
measuring techniques, for example measuring techniques based on the
principle of light diffraction.

[0046] Other techniques for determining particle sizes include, for
example, granulometry in which a uniform suspension of a small quantity
of the powder to be investigated is prepared in a suitable dispersion
medium and is then exposed to sedimentation. The percentage distribution
of the particle sizes can be estimated from the correlation between size
and density of the spherical particles and their sedimentation rate as
determined by Stokes law and the sedimentation time. Other methods for
determining particle size include microscopy, electron microscopy, sieve
analysis, sedimentation analysis, determination of the surface density
and the like.

[0047] The particle size data appearing in the present specification were
obtained in a well known manner with a standard test procedure employing
Stokes' Law of Sedimentation by sedimentation of the particulate material
in a fully dispersed condition in an aqueous medium using a Sedigraph
5100 machine as supplied by Micromeritics Instruments Corporation,
Norcross, Ga., USA (telephone: +1 770 662 3620; web-site:
www.micromeritics.com), referred to herein as a "Micromeritics Sedigraph
5100 unit".

[0048] Preferably talc is used as inorganic filler.

[0049] Before the talc is added it may be treated with various surface
treatment agents, such as organic titanate coupling agents, silane
coupling agents, fatty acids, metal salts of fatty acids, fatty acid
esters, and the like, in a manner known in the state of the art. The talc
may also be added without surface treatment.

[0050] Preferably the talc is added without surface treatment.

[0051] The amount of filler added to the heterophasic polymer composition
is about 3 to 25 wt %, preferably 5 to 15 wt %, based on the weight of
the polymer composition.

[0053] The expressions "multimodal" or "bimodal" or "unimodal" used herein
refers to the modality of the polymer, i.e. the form of its molecular
weight distribution curve, which is the graph of the molecular weight
fraction as a function of its molecular weight. As will be explained
below, the polymer components of the present invention are produced in a
sequential step process, using reactors in serial configuration and
operating at different reaction conditions. As a consequence, each
fraction prepared in a specific reactor will have its own molecular
weight distribution. When the molecular weight distribution curves from
these fractions are superimposed to obtain the molecular weight
distribution of the final polymer, that curve may show two or more maxima
or at least be distinctly broadened when compared with curves for the
individual fractions.

[0054] According to the present invention the heterophasic propylene
copolymer discussed above is produced in a multistage process, wherein
the polypropylene matrix (A) is produced at least in one slurry reactor
and subsequently the elastomeric copolymer (B) is produced at least in
one gas phase reactor.

[0055] A preferred multistage process is a slurry-gas phase process, such
as developed by Borealis and known as the Borstar® technology. In
this respect, reference is made to EP 0 887 379, WO 2004/000899, WO
2004/111095, WO 99/24478, WO 99/24479 and WO 00/68315 incorporated herein
by reference.

[0056] Preferably the heterophasic propylene copolymers with high levels
of impact strength/stiffness levels, combined with absolutely flow mark
free injection moulded parts according to the invention are produced in a
multistage process by using a special Ziegler-Natta procatalyst in
combination with an external donor and a cocatalyst, as described below
in detail.

[0057] Such a multistage process preferably comprises the steps of:
[0058] producing a polypropylene polymer matrix (A) in the presence of a
catalyst system, as described in detail below, comprising a special
Ziegler-Natta procatalyst in combination with the external donor and the
cocatalyst in at least one slurry reactor [0059] transferring the slurry
reactor product into a first gas phase reactor (GPR), [0060] wherein the
slurry reactor product is further polymerized in the presence of the
catalyst system in said first GPR [0061] transferring the first GPR
product into a 2nd GPR [0062] producing an
ethylene/propylene-copolymer (B) in the polymer matrix (A) in the
presence of the catalyst system in said 2nd GPR [0063] transferring
the 2nd GPR product into a 3rd GPR and further producing an
ethylene/propylene-copolymer (B) in the polymer matrix (A) in the
presence of catalyst system in said 3rd GPR, said ethylene/propylene
copolymers having the same composition ratios and [0064] recovering the
polymer product for further processing, yielding a polypropylene polymer
matrix (A) containing said ethylene/propylene copolymers (B) having the
same composition ratios, respectively having same ethylene content and
intrinsic viscosities, so that a unimodal rubber composition is obtained.

[0065] Preferably the process comprises also a prepolymerization step with
the chosen catalyst system, as described in detail below, comprising the
special Ziegler-Natta procatalyst, the external donor and the cocatalyst.

[0066] In a preferred embodiment, the prepolymerization is conducted as
bulk slurry polymerization in liquid propylene, i.e. the liquid phase
mainly comprises propylene, with minor amount of other reactants and
optionally inert components dissolved therein.

[0067] The prepolymerization reaction is typically conducted at a
temperature of 0 to 50° C., preferably from 10 to 45° C.,
and more preferably from 15 to 40° C.

[0068] The pressure in the prepolymerization reactor is not critical but
must be sufficiently high to maintain the reaction mixture in liquid
phase. Thus, the pressure may be from 20 to 100 bar, for example 30 to 70
bar.

[0069] The catalyst components are preferably all introduced to the
prepolymerization step. However, where the solid catalyst component (i)
and the cocatalyst (ii) can be fed separately it is possible that only a
part of the cocatalyst is introduced into the prepolymerization stage and
the remaining part into subsequent polymerization stages. Also in such
cases it is necessary to introduce so much cocatalyst into the
prepolymerization stage that a sufficient polymerization reaction is
obtained therein.

[0070] It is possible to add other components also to the
prepolymerization stage. Thus, hydrogen may be added into the
prepolymerization stage to control the molecular weight of the prepolymer
as is known in the art. Further, antistatic additive may be used to
prevent the particles from adhering to each other or to the walls of the
reactor.

[0071] The precise control of the prepolymerization conditions and
reaction parameters is within the skill of the art.

[0072] A slurry reactor designates any reactor, such as a continuous or
simple batch stirred tank reactor or loop reactor, operating in bulk or
slurry and in which the polymer forms in particulate form. "Bulk" means a
polymerization in reaction medium that comprises at least 60 wt %
monomer. According to a preferred embodiment the slurry reactor comprises
a bulk loop reactor.

[0074] With respect to the above-mentioned preferred slurry-gas phase
process, the following general information can be provided with respect
to the process conditions.

[0075] Temperature of from 40° C. to 110° C., preferably
between 50° C. and 100° C., in particular between
60° C. and 90° C., with a pressure in the range of from 20
to 80 bar, preferably 30 to 60 bar, with the option of adding hydrogen in
order to control the molecular weight in a manner known per se.

[0076] The reaction product of the slurry polymerization, which preferably
is carried out in a loop reactor, is then transferred to the subsequent
gas phase reactor, wherein the temperature preferably is within the range
of from 50° C. to 130° C., more preferably 60° C. to
100° C., at a pressure in the range of from 5 to 50 bar,
preferably 8 to 35 bar, again with the option of adding hydrogen in order
to control the molecular weight in a manner known per se.

[0077] The residence time can vary in the reactor zones identified above.
In one embodiment, the residence time in the slurry reactor, for example
a loop reactor, is in the range of from 0.5 to 5 hours, for example 0.5
to 2 hours, while the residence time in the gas phase reactor generally
will be from 1 to 8 hours.

[0078] If desired, the polymerization may be effected in a known manner
under supercritical conditions in the slurry, preferably loop reactor,
and/or as a condensed mode in the gas phase reactor.

[0079] According to the invention the heterophasic polypropylene
copolymers are obtainable by a multistage polymerization process, as
described above, in the presence of a catalyst system comprising [0080]
(i) a modified Ziegler-Natta procatalyst which contains a
trans-esterification product of a lower alcohol and a phthalic ester and
[0081] (ii) an organometallic cocatalyst and [0082] (iii) an external
donor

[0083] The procatalyst used according to the invention is prepared by
[0084] a) reacting a spray crystallized or emulsion solidified adduct of
MgCl2 and a C1-C2 alcohol with TiCl4[0085] b)
reacting the product of stage a) with a dialkylphthalate of formula (I)

[0085] ##STR00001## [0086] wherein R1' and R2' are
independently at least a C5 alkyl [0087] under conditions where a
transesterification between said C1 to C2 alcohol and said
dialkylphthalate of formula (I) takes place to form the internal donor
[0088] c) washing the product of stage b) or [0089] d) optionally
reacting the product of step c) with additional TiCl4

[0090] The procatalyst is produced as defined for example in the patent
applications WO 87/07620, WO 92/19653, WO 92/19658 and EP 0 491 566. The
content of these documents is herein included by reference.

[0091] First an adduct of MgCl2 and a C1-C2 alcohol of the
formula MgCl2*nROH, wherein R is methyl or ethyl and n is 1 to 6, is
formed. Ethanol is preferably used as alcohol.

[0092] The adduct, which is first melted and then spray crystallized or
emulsion solidified, is used as catalyst carrier.

[0093] In the next step the spray crystallized or emulsion solidified
adduct of the formula MgCl2*nROH, wherein R is methyl or ethyl,
preferably ethyl and n is 1 to 6, is contacting with TiCl4 to form a
titanised carrier, followed by the steps of [0094] adding to said
titanised carrier [0095] (i) a dialkylphthalate of formula (I) with
R1' and R2' being independently at least a C5-alkyl, like
at least a C8-alkyl, [0096] or preferably [0097] (ii) a
dialkylphthalate of formula (I) with R1' and R2' being the same
and being at least a C5-alkyl, like at least a C8-alkyl [0098]
or more preferably [0099] (iii) a dialkylphthalate of formula (I)
selected from the group consisting of propylhexylphthalate (PrHP),
dioctylphthalate (DOP), di-iso-decylphthalate (DIDP), and
ditridecylphthalate (DTDP), yet more preferably the dialkylphthalate of
formula (I) is a dioctylphthalate (DOP), like di-iso-octylphthalate or
diethylhexylphthalate, in particular diethylhexylphthalate, [0100] to
form a first product [0101] subjecting said first product to suitable
transesterification conditions, i.e. to a temperature between 100 to
150° C., such that said methanol or ethanol is transesterified
with said ester groups of said dialkylphthalate of formula (I) to form
preferably at least 80 mol-%, more preferably 90 mol-%, most preferably
95 mol.-%, of a dialkylphthalate of formula (II)

[0101] ##STR00002## [0102] with R1 and R2 being methyl or
ethyl, preferably ethyl, [0103] the dialkylphthalat of formula (II) being
the internal donor and [0104] recovering said transesterification
product as the procatalyst composition.

[0105] The adduct of the formula MgCl2*nROH, wherein R is methyl or
ethyl and n is 1 to 6, is in a preferred embodiment melted and then the
melt is preferably injected by a gas into a cooled solvent or a cooled
gas, whereby the adduct is crystallized into a morphologically
advantageous form, as for example described in WO 87/07620.

[0106] This crystallized adduct is preferably used as the catalyst carrier
and reacted to the procatalyst useful in the present invention as
described in WO 92/19658 and WO 92/19653.

[0107] The transesterification is performed at a temperature above
100° C., advantageously between 130 to 150° C.

[0108] As the catalyst residue is removed by extracting, an adduct of the
titanised carrier and the internal donor is obtained, in which the group
deriving from the ester alcohol has changed.

[0109] In case sufficient titanium remains on the carrier, it will act as
an active element of the procatalyst.

[0110] Otherwise the titanization is repeated after the above treatment in
order to ensure a sufficient titanium concentration and thus activity.

[0111] Preferably the procatalyst used according to the invention contains
2.5% by weight of titanium at the most, preferably 2.2% by weight at the
most and more preferably 2.0% by weight at the most. Its donor content is
preferably between 4 to 12% by weight and more preferably between 6 and
10% by weight.

[0112] More preferably the procatalyst used according to the invention has
been produced by using ethanol as the alcohol and dioctylphthalate (DOP)
as dialkylphthalate of formula (I), yielding diethyl phthalate (DEP) as
the internal donor compound (prepared according to WO92/19653 as
disclosed in WO 99/24479; especially with the use of dioctylphthalate as
dialkylphthalate of formula (I) according to WO 92/19658) or the catalyst
Polytrack 8502, commercially available from Grace.

[0113] The Ziegler-Natta procatalyst is modified by polymerizing a vinyl
compound in the presence of the catalyst system, comprising the special
Ziegler-Natta procatalyst, an external donor and optionally a cocatalyst,
which vinyl compound has the formula:

CH2═CH--CHR6R7

wherein R6 and R7 together form a 5- or 6-membered saturated,
unsaturated or aromatic ring or independently represent an alkyl group
comprising 1 to 4 carbon atoms, and the modified catalyst is used for the
preparation of the polymer composition. The polymerized vinyl compound
can act as a nucleating agent.

[0115] Concerning the modification of catalyst reference is made to the
international applications WO 99/24478, WO 99/24479 and particularly WO
00/68315, incorporated herein by reference with respect to the reaction
conditions concerning the modification of the catalyst as well as with
respect to the polymerization reaction.

[0116] For the production of the heterophasic propylene copolymers
according to the invention the catalyst system used comprises in addition
to the special Ziegler-Natta procatalyst an organometallic cocatalyst as
component (ii). Accordingly it is preferred to select the cocatalyst from
the group consisting of trialkylaluminium, like triethylaluminium (TEA),
dialkyl aluminium chloride and alkyl aluminium sesquichloride.

[0117] Component (iii) of the catalysts system used is an external donor
represented by formula (III)

Si(OCH2CH3)3(NR1R2)

wherein R1 and R2 can be the same or different a represent a
hydrocarbon group having 1 to 12 carbon atoms.

[0118] R1 and R2 are independently selected from the group
consisting of linear aliphatic hydrocarbon group having 1 to 12 carbon
atoms, branched aliphatic hydrocarbon group having 1 to 12 carbon atoms
and cyclic aliphatic hydrocarbon group having 1 to 12 carbon atoms. It is
in particular preferred that R1 and R2 are independently
selected from the group consisting of methyl, ethyl, n-propyl, n-butyl,
octyl, decanyl, iso-propyl, iso-butyl, iso-pentyl, tert.-butyl,
tert.-amyl, neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl and
cycloheptyl.

[0119] More preferably both R1 and R2 are the same, yet more
preferably both R1 and R2 are an ethyl group.

[0120] Most preferably diethylaminotriethoxysilane is used as external
donor.

[0121] The external donor may be produced according to the methods
disclosed in EP 1538 167.

[0122] The content of this document is herein included by reference.

[0123] The external donor may also be represented by the formula (IV)

R3nR4mSi(OR5)z (IV))

wherein R3 and R4 are identical or different hydrocarbon
residues, R5 is methyl or ethyl, z is 2 or 3, preferably 2; m is 0
or 1; n is 0 or 1; with the proviso that n+m+z=4.

[0124] Preferably R3 and R4 are independently selected from the
group consisting of linear aliphatic hydrocarbon group, branched
aliphatic hydrocarbon group, cyclic aliphatic hydrocarbon group and
aromatic group. It is in particular preferred that R3 and R4
are independently selected from the group consisting of methyl, ethyl,
propyl, butyl, octyl, decanyl, iso-propyl, iso-butyl, iso-pentyl,
tert.-butyl, tert.-amyl, neopentyl, cyclopentyl, cyclohexyl,
methylcyclopentyl and cycloheptyl. In a preferred embodiment the external
donor has the formula V

R3R4Si(OR5)2 (V)

wherein R3 and R4 are identical or different hydrocarbon
residues, with the proviso that [0125] (a) R3 is a branched
aliphatic hydrocarbon group or cyclic aliphatic hydrocarbon group,
preferably selected from the group consisting of iso-propyl, iso-pentyl,
tert.-butyl, tert.-amyl, neopentyl, cyclopentyl, cyclohexyl,
methylcyclopentyl and cycloheptyl, and [0126] (b) R4 is selected
from the group consisting of linear aliphatic hydrocarbon group, branched
aliphatic hydrocarbon group and cyclic aliphatic hydrocarbon group,
preferably selected from the group consisting of methyl, ethyl, propyl,
butyl, octyl, decanyl, iso-propyl, iso-butyl, iso-pentyl, tert.-butyl,
tert.-amyl, neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl and
cycloheptyl.

[0127] Accordingly it is preferred that the external donor is selected
from the group consisting of di-iso-propyldiethoxysilane (DI P DES),
cyclohexylmethyldiethoxysilane (CH MDES), dicyclopentyldimethoxysilane
(DCPDMS), cyclohexylmethyl-dimethoxysilane (CHMDMS) and
dicyclopentadienyldiethoxysilane (DCPDES). More preferably an external
donor selected from DCPDMS-donor, CHMDMS-donor and
di-iso-propyldiethoxysilane (DIPDES) is used and most preferably the
DCPDMS-donor is used.

[0128] The current invention also provides a multistage process as
described above for producing to the polypropylene matrix (A), containing
the elastomeric copolymer (B) using the special catalyst system
comprising components (i), (ii) and (iii).

[0129] Components (C) and (D) of the heterophasic polymer composition
according to the invention are added to the polypropylene matrix (A),
containing the elastomeric copolymer (B) which is collected from the
final reactor of the series of reactors.

[0130] The heterophasic polymer composition of the invention may further
contain various conventional additives, such as antioxidants,
UV-stabilizers, acid scavengers, lubricants, demoulding agents,
nucleating agents, colouring agents, etc. in an amount of 0.001 to 10 wt.
%, preferably up to 5.0 wt % and more preferably up to 3.0 wt % based on
the weight of the heterophasic polypropylene composition.

[0131] Components (C) and (D) and the optional additives are mixed into
the composition prior to or during the extrusion process in a one-step
compounding process. Alternatively, a master batch may be formulated,
wherein the heterophasic propylene copolymer is first mixed with only
some of the additives.

[0132] For mixing, a conventional compounding or blending apparatus, e.g.
a Banbury mixer, a t-roll rubber mill, Buss-co-kneader or a twin screw
extruder may be used. The polymer materials recovered from the extruder
are usually in the form of pellets. These pellets are then preferably
further processed, e.g. by injection moulding to generate articles and
products of the inventive heterophasic propylene copolymers.

[0133] Heterophasic polypropylene compositions according to the invention
may be pelletized and compounded using any of the variety of compounding
and blending methods well known and commonly used in the resin
compounding art.

[0134] The compositions of the current invention are preferably used for
the production of moulded articles, preferably injection moulded
articles. Even more preferred is the use for the production of automotive
parts, like bumpers, spoilers, fenders, body panels, side bump strips and
the like.

[0135] The current invention also provides articles comprising the
inventive heterophasic polypropylene compositions with high levels of
impact strength/stiffness levels, combined with absolutely flow mark free
injection moulded parts. Preferably, these articles are produced by
injection moulding.

[0136] Surprisingly, it was found that the molded articles manufactured
with the heterophasic polypropylene compositions prepared according to
the invention display excellent surface quality.

[0137] The surface quality of injection molded parts, which is determined
according to the procedure described in the experimental section, must be
"excellent", i.e. only polymer compositions which can be injection molded
without showing any flow mark, solve the problem which is underlying the
present invention.

[0138] In the following the present invention is further illustrated by
means of examples.

Methods:

a) Melt Flow Rate

[0139] Unless otherwise specified, the melt flow rate was measured as the
MFR2 in accordance with ISO 1133 (230° C., 2.16 kg load) for
polypropylene and is indicated in g/10 min. The MFR is an indication of
the flowability, and hence the processability, of the polymer. The higher
the melt flow rate, the lower the viscosity of the polymer.

b) Comonomer content was measured with Fourier transform infrared
spectroscopy (FTIR) calibrated with 13C-NMR. When measuring the
ethylene content in polypropylene, a thin film of the sample (thickness
about 250 mm) was prepared by hot-pressing. The area of --CH2--
absorption peak (800-650 cm-1) was measured with Perkin Elmer FTIR
1600 spectrometer. The method was calibrated by ethylene content data
measured by 13C-NMR. c) Flexural modulus was measured according to
ISO 178 by using injection molded test specimens as described in EN ISO
1873-2 (80×10×4 mm)

d) Tensile Modulus

[0140] The tensile modulus was measured according to ISO 572-3 at 1 mm/min
and 23° C. Test specimens as described in EN ISO 1873-2
(80×10×4 mm) were used.

[0141] e) Xylene Solubles

[0142] The xylene soluble fraction (XS) as defined and described in the
present invention was determined as follows: 2.0 g of the polymer were
dissolved in 250 mm p-xylene at 135° C. under agitation. After 30
minutes, the solution was allowed to cool for 15 minutes at ambient
temperature and then allowed to settle for 30 minutes at
25±0.5° C. The solution was filtered with filter paper into two
100 mm flasks. The solution from the first 100 mm vessel was evaporated
in nitrogen flow and the residue dried under vacuum at 90° C.
until constant weight is reached. The xylene soluble fraction (percent)
can then be determined as follows:

[0143] The intrinsic viscosity (IV) value increases with the molecular
weight of a polymer. The IV values e.g. of the amorphous phase were
measured according to ISO 1628/1 (October 1999) in Decalin at 135°
C.

g) Charpy Notches Impact Strength (NIS),

[0144] NIS was determined according to ISO 179-1eA:2000 on V-notched
samples of 80×10×4 mm3 at +23° C. (Charpy notched
impact strength (23° C.)), and -20° C. (Charpy notched
impact strength (-20° C.)). The test specimens were prepared by
injection moulding using a IM V 60 TECH machinery in line with ISO
1872-2. The melt temperature was 200° C. and the mold temperature
was 40° C.

h) Flow Properties (Spiral Flow at 230° C.)

[0145] Spiral Test was carried out using an Engel ES330/65 cc90 injection
molding apparatus with a spiral mould and pressure of 1000 MPa

[0146] The spiral flow length can be determined immediately after the
injection operation.

EXAMPLES

Preparation of Base Resins A, B and C According to the Invention and as
Comparative Examples Base Resins D and E

[0147] The inventive and comparative examples were prepared in a connected
series of reactors. The Base resins A, B, C, D and E were produced using
Borstar® technology in a plant having a prepolymerization reactor, a
loop reactor and three fluid bed gas-reactors connected in series. The
catalyst used in the polymerization was a Vinylcyclohexyl (VHC)-modified
catalyst prepared according to Example 1 of WO99/24479, the cocatalyst
was Triethylaluminium (TEA) and as an external donor ED dicyclopentyl
dimethoxy silane was used.

[0148] After a first pre-polymerization step the catalyst system was fed
to the slurry reactor, where the polymerization of the polypropylene
homopolymer matrix phase was initiated. The slurry phase loop reactor was
then followed by a first gas phase reactor (1st GPR) in series, in
which the matrix phase of the polypropylene homopolymer was completed.
After transfer to a second gas phase reactor (2nd GPR) the
elastomeric rubber disperse phase was produced by copolymerization of
propylene with ethylene comonomer. The reaction product of the second gas
phase reactor was then transferred into a third gas phase reactor
(3rd GPR) wherein the ethylene/propylene copolymer was completed.

[0152] The mixtures were compounded by feeding the components to a Prism
24twin-screw extruder (Prism Ltd., Staffordshire, UK). The material was
then extruded through a strand die, cooled and chopped to form pellets.

[0153] An optical measurement system, as described for example by Sybille
Frank et al. in PPS 25 Intern. Conf. Polym. Proc. Soc 2009 or Proceedings
of the SPIE, Volume 6831, pp 68130T-68130T-8 (2008) was used for
characterizing the surface quality.

[0154] This method consists of two aspects:

1. Image Recording:

[0155] The basic principle of the measurement system is to illuminate the
plates with a defined light source (LED) in a closed environment and to
record an image with a CCD-camera system.

A Schematic Setup is Given in FIG. 1.

2. Image Analysis:

[0156] The specimen is floodlit from one side and the upwards reflected
portion of the light is deflected via two mirrors to a CCD-sensor. The so
created grey value image is analyzed in lines. From the recorded
deviations of grey values the mean square error (MSE) is calculated
allowing a quantification of surface quality, i.e. the larger the MSE
value the more pronounced is the surface defect.

[0157] Table 5 provides an overview of MSE-values and the corresponding
visual ranking of the surface quality of injection moulded grained
plaques.

[0158] According to the visual ranking judged visually by a tester the
tigerskin level was assessed by a number between 0 (no flow mark
"excellent) and 5 (flow marks are visible, "insufficient).